Microscopes are generally equipped with an objective lens revolver (revolver) that houses two or more different objective lenses. The desired objective lens is turned into the optical path of the microscope by rotating the revolver. The objective lenses are focused by moving the stage along the optical path of the objective lens of the microscope. As is well known, the body of the microscope expands due to rises in ambient temperature, changing the distance between the stage including the prepared specimen being viewed and the objective lens beyond the depth of focus (in microns). This causes undesirable results such as the loss of the focused position (state) that was adjusted at ordinary temperature.
In conventional optical measuring instruments and optical microscopes, the objective lens (the key component of such optical equipment) has a temperature dependency of about one 1 μm per ° C., the hardware supporting the objective lens is asymmetrical to the optical axis, and is temperature dependent. Furthermore, the stage and sample positioning mechanism are unbalanced because it is extremely asymmetrical to the optical axis in weight and shape, causing the focus to be unstable against temperature fluctuations and also causing the object point to drift.
A temperature fluctuation of 0.1° C. is unavoidable even when the room temperature is controlled. When the temperature dependency of the object lens is 1.0 μm per 1° C. , a drift of 100 nm will result per each temperature fluctuation of 0.1° C., causing unstable focusing.
Due to the above out-of-focus conditions, conventional optical microscopes cannot meet the precision requirements for measuring the position of molecules or molecular motion. This invention aims to realize an optical microscope of high stability in which the image of the sample does not become out of focus during observation, and movement (drift) of the object point (object) does not occur.
This invention intends to improve the focusing stability of the microscope by directly fixing the objective lens, the sample-positioning stage, and the focusing mechanism symmetrical in weight and shape to the center of the optical axis, and by manufacturing and assembling the above configuration with components that have the lowest temperature dependencies, or by configuring the components so that the sum of the temperature dependencies of the individual components is equivalent and the total length of balance of the above units is equal. Focusing stability provided by this invention refers to the stability of the relative positions of the focusing position of the object lens and the object point on the X, Y, and Z axes independently of environmental conditions.
Components with an extremely small temperature dependency include the stage unit made of Invar (steel of specific components of iron, carbon, and chrome), with the objective lens of the microscope made of glass and metal that have an extremely small temperature dependency. Optical equipment manufactured from the above materials would be very expensive. To reduce the manufacturing cost, the temperature dependencies are eliminated using special compensating mechanisms.